Abstract

Optical coherence tomography angiography (OCTA) is a well-established non-invasive retinal vascular imaging technique. It has been recently adapted to image the anterior segment and has shown good potential to image corneal vascularisation. The purpose of the study is to evaluate the usefulness of OCTA to monitor regression of corneal vessels following anti-VEGF (vascular endothelial growth factor) treatment using a previously established corneal vascularisation rabbit model. The regression of vessels following the treatment with aflibercept and ranibizumab anti-VEGFs using both topical instillation and sub-conjunctival injection was quantified using OCTA and compared with ICGA (indocyanine green angiography). Overall vessel density measurements using OCTA showed good correlation (r = 0.988, p < 0.001) with ICGA, with no significant difference between the two treatment groups (p = 0.795). It was also shown that OCTA provided good repeatability outcomes of the quantitative measurements. Using Bland-Altman plots, vessel growth density values between anti-VEGF treatments were compared to control saline group. It was observed that aflibercept provided longer lasting effect than ranibizumab. We also observed that in both drugs, the topical route of administration topical provided longer regression outcomes compared to one-time sub-conjunctival injection. Thereby, with this pilot study, it was demonstrated that OCTA is a reliable imaging technique to follow-up and monitor corneal vascularisation and its treatment quantitatively.

Highlights

  • Anti-vascular endothelial growth factor therapies are effective and well-tolerated medications that have revolutionized the treatment of retinal conditions such as neo-vascular age-related macular degeneration and macular oedema in diabetic retinopathy or retinal vein occlusions[10]

  • We have previously described the use of ASOCTA as a quantitative diagnostic tool for corneal vascularization in a rabbit model, where we compared it to ICGA and slit lamp bio-microscopy, demonstrating good repeatability and better vessel delineation than other conventional techniques[12]

  • We found good agreement of vessel density measurements between ASOCTA and ICGA, as demonstrated by the Bland-Altman plots of mean vessel growth density (%) values from ASOCTA (1.285 ± 9.248%) and ICGA (1.339 ± 9.248%) within 95% limits of agreement (LOA) – Fig. 1

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Summary

Introduction

Anti-vascular endothelial growth factor (anti-VEGF) therapies are effective and well-tolerated medications that have revolutionized the treatment of retinal conditions such as neo-vascular age-related macular degeneration and macular oedema in diabetic retinopathy or retinal vein occlusions[10]. There have been a few studies comparing the efficacy of topical and sub-conjunctival anti-VEGF route administration for the treatment of corneal vascularisation, direct comparisons between ranibizumab and aflibercept are lacking[17,18]. Reliable and objective tools for the imaging of corneal vascularization treatment have not been studied for anti-VEGF therapies. We have previously described the use of ASOCTA (anterior segment optical coherence tomography angiography) as a quantitative diagnostic tool for corneal vascularization in a rabbit model, where we compared it to ICGA and slit lamp bio-microscopy, demonstrating good repeatability and better vessel delineation than other conventional techniques[12].

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